Embryology Flashcards
Give some other names for pharyngeal arches
Pharyngeal apparatus
Bronchial arches
When does the neural tube form?
Week 3
By which time has the embryo folded?
End of week 4
What tissues forms the core of the pharyngeal arches?
Mesoderm
What are the pharyngeal pouches?
Inner pocketings of primitive gut tube
Endoderm lined
What do the pharyngeal pouches develop into?
Middle ear
Parathyroids, thymus and palatine tonsils
Where do the parts of the pharynx run from and to?
Nasal = base of skull to soft palate Oral = soft palate to larynx Laryngeal = posterior to larynx to inferior border of cricoid cartilage
How many pharyngeal arches are there?
5 in total
1, 2, 3, 4 and 6
What are pharyngeal clefts?
External pocketings of arches
Ectoderm lined
What do we call the 3 vesicles of the brain?
Prosencephalon = forebrain Mesencephalon = midbrain Rhombencephalon = hindbrain
How many cranial nerves are there?
12 pairs
Which cranial nerves innervate the pharyngeal arches?
V, VII, IX and X
What is the face derived from?
The frontonasal prominence and the 1st pharyngeal arch
Which arch gives us the muscles of mastication?
Pharyngeal arch 1
Which nerve innervate pharyngeal arch 1?
Trigeminal nerve
Which arch gives us the muscles of facial expression?
Arch 2
Which nerve innervates pharyngeal arch 2?
Facial nerve
What are the muscle derivatives of the 3rd arch?
Stylopharyngeus
What are the muscle derivatives of the 4th arch?
Cricothyroid
Levator palatini
Constrictors of pharynx
What are the muscle derivatives of 6th arch?
Intrinsic muscles of larynx
What is the principle sensory nerve of the head?
Trigeminal nerve (V)
What does the facial nerve pass through into the face?
Stylomastoid foramen
Parotid gland
What is the stylopharyngeus muscle?
Between styloid process and pharynx
Elevates the larynx and pharynx
Dilates the pharynx to permit passage of large food bolus
What nerve innervates the third arch?
Glossopharyngeal nerve (IX)
Which arch does the vagus nerve innervate?
4th and 6th
Where do the different cartilages come from?
Meckel’s = 1st arch
Reichert’s = 2nd arch
Cartilage of larynx = 4th and 6th arches
What does Meckel’s cartilage develop into?
Provides template for mandible
Malleus and incus
What does Reichert’s cartilage develop into?
Stapes
Styloid process
Hyoid bone
What cartilages come from the 4th and 6th arches?
Thyroid
Arytenoid
Cricoid
What is the artery of the 3rd arch?
Internal carotid artery
What are the arteries of the 4th arch?
Arch of aorta and brachiocephalic
What are the arteries of the 6th arch?
Pulmonary arch
What does the 2nd pouch develop into?
Palatine tonsils
What do the 3rd and 4th pouches develop into?
3rd and 4th dorsal = parathyroids
3rd ventral = thymus gland
What does the 1st pouch develop it?
Primitive tympanic cavity
What does the 1st cleft develop into?
External auditory meatus
Where does the Eustachian tube run from and to?
Middle ear to nasopharynx
What are the major features of the face?
Palpebral fissures
Oral fissure
Nares
Philtrum
What is a philtrum?
Groove on the upper lip
The facial skeleton is derived from which cells?
Neural crest cells of 1st pharyngeal arch
The muscles of mastication are derived from which cells?
Mesoderm of 1st pharyngeal arch
What is the nerve of the 1st pharyngeal arch?
Trigeminal (V)
What is the nerve of the 2nd pharyngeal arch?
Facial (VII)
Which cells are the muscles of facial expression derived from?
Mesoderm of 2nd pharyngeal arch
What are nasal placodes?
Dents in the frontonasal prominence (FNP) where the organ of special sense (olfaction) will develop
What is the stomatodeum?
Small depression in head with buccopharyngeal membrane in centre
Avascular membrane that ruptures to form the oral fissure
What are the names of the 2 parts of the 1st pharyngeal arch?
Maxillary prominence
Mandibular prominence
Which features have their origin from the FNP?
Forehead
Bridge of nose
Nose
Philtrum
Which facial features have their origin from maxillary prominence of 1 pharyngeal arch?
Cheeks
Lateral part upper lip
Lateral upper jaw
What facial features have origin of mandibular prominence of 1st pharyngeal arch?
Lower lip
Lower jaw
Where do medial and lateral nasal prominences form?
Either side of nasal placodes
2 medial, 2 lateral
Describe the development of the nasal prominences
Maxillary prominences grow medially pushing nasal prominences closer together
Medial nasal prominences fuse with each other
Medial nasal prominences fuse with maxillary prominences
Creates the intermaxillary segment
What compromises the intermaxillary segment?
Philtrum
4 incisors of upper jaw
Primary palate
What is the secondary palate derived from?
Palatal shelves
These derived from maxillary prominences
What is the oronasal membrane?
CT that ruptures to give a connection between the nasal and oral cavity
What does the nasal septum fuse with?
Secondary palate
How does a lateral cleft lip occur?
Failure of fusion of medial nasal prominence and maxillary prominence
How does a cleft lip and palate occur?
Failure of fusion of medial nasal prominence and maxillary prominence
And failure of palatal shelves to meet in midline
Eyes begin development in which week?
4
How does the eye develop?
Optic vesicles grows to surface
Makes contact with lens placode
Placode invaginates to create a vesicle
Forebrain forms the retina
How do the eyes move from lateral to frontal?
As the facial prominence grows
What is binocular vision?
Vision using 2 eyes
With overlapping fields of vision allowing good depth perception
The external auditory meatus is derived from …
1st pharyngeal cleft
Where do ears initially develop?
Inferior to mandible in the neck
As mandible grows the ears move up
Which placode leads to hearing and balance?
Otic placode
What features might be seen in a child with foetal alcohol syndrome?
Smaller head (impaired brain development) Lower nasal bridge Smaller eye openings Flat midface Short nose Thin upper lip
What parts of development are most sensitive to alcohol?
Neural crest migration
Brain development
What is ARND?
Alcohol related neurodevelopmental disorder
Milder version of FAS - less alcohol consumed during the pregnancy
What is the prevalence of FAS and ARND combined?
1 in 100 births